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// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
#include "runtime.h"
#include "os.h"
int8 *goos = "plan9";
void
runtime·minit(void)
{
}
void
runtime·osinit(void)
{
}
void
runtime·goenvs(void)
{
}
void
runtime·initsig(int32 queue)
{
}
void
runtime·exit(int32)
{
runtime·exits(nil);
}
void
runtime·newosproc(M *m, G *g, void *stk, void (*fn)(void))
{
USED(m, g, stk, fn);
m->tls[0] = m->id; // so 386 asm can find it
if(0){
runtime·printf("newosproc stk=%p m=%p g=%p fn=%p rfork=%p id=%d/%d ostk=%p\n",
stk, m, g, fn, runtime·rfork, m->id, m->tls[0], &m);
}
if (runtime·rfork(RFPROC | RFMEM, stk, m, g, fn) < 0 )
runtime·throw("newosproc: rfork failed");
}
// Blocking locks.
// Implement Locks, using semaphores.
// l->key is the number of threads who want the lock.
// In a race, one thread increments l->key from 0 to 1
// and the others increment it from >0 to >1. The thread
// who does the 0->1 increment gets the lock, and the
// others wait on the semaphore. When the 0->1 thread
// releases the lock by decrementing l->key, l->key will
// be >0, so it will increment the semaphore to wake up
// one of the others. This is the same algorithm used
// in Plan 9's user-level locks.
void
runtime·lock(Lock *l)
{
if(m->locks < 0)
runtime·throw("lock count");
m->locks++;
if(runtime·xadd(&l->key, 1) == 1)
return; // changed from 0 -> 1; we hold lock
// otherwise wait in kernel
while(runtime·plan9_semacquire(&l->sema, 1) < 0) {
/* interrupted; try again */
}
}
void
runtime·unlock(Lock *l)
{
m->locks--;
if(m->locks < 0)
runtime·throw("lock count");
if(runtime·xadd(&l->key, -1) == 0)
return; // changed from 1 -> 0: no contention
runtime·plan9_semrelease(&l->sema, 1);
}
void
runtime·destroylock(Lock *l)
{
// nothing
}
// User-level semaphore implementation:
// try to do the operations in user space on u,
// but when it's time to block, fall back on the kernel semaphore k.
// This is the same algorithm used in Plan 9.
void
runtime·usemacquire(Usema *s)
{
if((int32)runtime·xadd(&s->u, -1) < 0)
while(runtime·plan9_semacquire(&s->k, 1) < 0) {
/* interrupted; try again */
}
}
void
runtime·usemrelease(Usema *s)
{
if((int32)runtime·xadd(&s->u, 1) <= 0)
runtime·plan9_semrelease(&s->k, 1);
}
// Event notifications.
void
runtime·noteclear(Note *n)
{
n->wakeup = 0;
}
void
runtime·notesleep(Note *n)
{
while(!n->wakeup)
runtime·usemacquire(&n->sema);
}
void
runtime·notewakeup(Note *n)
{
n->wakeup = 1;
runtime·usemrelease(&n->sema);
}
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